Relieving attachment for machine tools



Dec. 7, 1943. E. A. WALKER RELIEVING ATTACHMENT FOR MACHINE TOOLS 2Sheets-Sheet l Filed Aug. 20, 1942 jgz Dec'. 7, 1943. E. A. WALKER2,336,201

RELIEVI NG ATTACHMENT FOR MACHINE TOOLS Filed Aug. 20, .1942 2Sheets-Sheet 2 Patented Dec. 7, 1 943 RELIEVING ATTACHMENT FOR MACHINETOOLS Ernest A. Walker, Worcester, Mass, assignor to John Bath &Company, Worcester, Mass, a corporation of Massachusetts ApplicationAugust 20, 1942, Serial No. 455,491

3 Claims.

This invention relates to machine tools, such as lathes and grindingmachines, which are adapted for use in the manufacture of taps orsimilar articles having relieved surfaces.

In such manufacture, it has been proposed to shift the work radiallyrelative to the cutting tool or grinding wheel to produce the desiredrelieving effect. All such proposals have, however, involved the use ofrelatively moving bearing surfaces and the relative movements have beenso slight, such as one or two thousandths of an inch, that effectivelubrication of the coacting surfaces has proved impractical.

It is the general object of my invention to provide an improvedsupporting structure for a re-.

lieving attachment, so formed that relatively moving bearing surfacesare entirely avoided.

To the accomplishment of this general object, I provide a relievingattachment in which the moving structure, such as the tail stock, ismounted on a rigidly clamped. but slightly flexible supporting member.Slight oscillatory movements of the tail stock are made possible byflexing said supporting member.

My invention further relates to arrangements and combinations of partswhich will be hereinafter described and more particularly pointed out inthe appended claims.

A preferred form of the invention is shown in the drawings, in whichFig. 1 is a plan view of a tail stock embodying my improvements;

Fig. 2 is a sectional front elevation, taken along the line 2-2 in Fig.1;

Fig. 3 is a side elevation, partly in section, and looking in thedirection of the arrow 3 in Fig. 1;

Fig. 4 is a detail sectional rear elevation, taken along the line 4-4 inFig. 3; r

Fig. 5 is a fragmentary rear elevation, looking in the direction of thearrow 5 in Fig. 3; and

Fig. 6 is a diagrammatic view illustrating the relieving action.

Referring to Figs. 1, 2 and 3, I have shown portions of a machinespecially designed for grinding taps and comprising a transverse slide(Fig. 3) supporting a tail stock base II which is adjustablelongitudinally of the slide l0 and which may be held in adjustedposition by a clamping bolt 12.

The tail center I4 is mounted in a rectangular bar I slidablelongitudinally in the tail stock IS. The bar I5 is movable axially inthe tail stock to engage the work, shown herein as a tap T. The bar 15may be moved by a pinion I1 operated by a handle It, all of these partsbeing of the usual construction.

The tail stock It is provided with a rigid depending portion 20 (Fig. 3)which is slotted to snugly receive the upper edge of an axiallyextendedflat spring plate 2|, which plate is rigidly clamped to the tail stockportion 20 by clamping screws 22 (Fig. 5).

The lower edge portion of the spring plate 2| abuts shoulders 24 and 25(Fig. 3) in the tail stock base II and is rigidly held in position by aclamping bar 26 and a plurality of clamping screws 21.

The tail stock I6 is thus firmly supported on the tail stock base H butis capable of making slight swinging or'oscillatory movements relativeto the base II by flexing the spring plate 2|. Such slight oscillatorymovements will swing the associated end of the tap T intermittentlyrearward to relieve the cutting teeth of the tap, as will be hereinafterdescribed.

In order to produce these slight oscillatory movements, I provide a cam30 (Fig. 3) mounted on a driving shaft 3| (Fig. 2) which is rotated intimed relation to the rotation of the tap T.

In the drawing, the cam 30 (Fig. 3) is shown as having four lobes andthe tap is shown as having four lands, and the driving connections willbe such that the tap T and the driving shaft 3| rotate at the samespeed.

The cam 30 is engaged by a cam roll 33 (Figs. 2 and 3) mounted in a camlever 34 pivoted at 35 (Fig. 3) to the tail stock IS. The cam lever 34can swing vertically within rather close limits and has an upwardprojection 40 engaging a wedge 4| held in position by a clamping stud 42extending through a slot 43 in the tail stock l6 and provided with aclamping nut 44.

The cam lever 34 and wedge 41 thus transmit oscillatory movements fromth cam 39 to the tail stock 16, and as the front end of the tail stockis raised and lowered, the tail center l4 (being directly over thespring plate 2|) will be moved slightly rearward and forward.

The normal grinding position is the forward position, which ispositively determined by engagement of bearing surfaces 50 (Figs. 3 and4) with the upper surface 5| (Fig. 4) of a sliding wedge 52. The wedge52 is seated on an inclined bearing surface 53 and may be moved alongsaid inclined surface by adjusting screws 54 and 55, the adjustmentbeing retained by lock nuts 56.

The ends of the wedge 52 are beveled, as well shown in Fig. 4, so thatthe forces applied by the clamping screws 54 and 55 will firmly seat thewedge on the inclined surface 53. By adjusting the wedge 52 lengthwise,this will determine whether the work is to be straight or tapered.

A rubber block 60 (Fig. 3) may be inserted between shoulders GI and 62in the front upper portion of the tail stock I6 and coacting surfaces inthe fixed drive shaft casing 65. The block 60 acts as a spring orcushion to normally seat the wedge M (Fig. 3) on the lever extension 40,and the bearing surfaces 50 on the wedge 52, thus returning the parts tonormal grinding position.

In Fig. 6 I have shown diagrammatically the relative positions of thetap T and the grinding wheel W during the grinding and relieving of atap. In the upper part of Fig. 6, the work is; in forward or normalgrinding position, corresponding to the position of the parts shown inFig. 4

and with the regular grinding of the tap teeth taking place.

In the lower part of Fig. 6, the tap T has been moved slightly rearward,so that the following ends of the tap teeth will be slightly relievedfor clearance. A separate relieving movement must be produced for eachand every tooth on each land of the tap, which with a four-flute tap asshown would be four times per revolution, corresponding to the fourlobes of the cam 3E3.

It willbe understood that the relieving action is greatly exaggerated inFig. 6, the actual movement commonly being not over one or twothousandths of an inch and frequently less. By withdrawing the wedge 2!,10st motion between the cam 30 and cam roll 33 may be introduced and thepoint of beginning of the relieving action may be delayed.

The steel plate 2| is thus subject to extremely slight flexure and maybe relatively thick and rigid, so as to firmly support the tail stockand to remain operative throughout a long period of use.

By the use of the construction above described, the tail stock ismovably supported without the use of any relatively movable bearingsurfaces whatever, so that the problem of lubricating bearing surfaceshaving exceedingly slight relative movements is entirely avoided.

Having thus described my invention and the advantages thereof, I do notwish to be limited to the details herein disclosed, otherwise than asset forth in the claims, but what I claim is:

'1. In, amachine tool, a work support, a base, a rigidly secured butslightly flexible connection between said work support and said base,means to oscillate said work support on said flexible connection andrelative to said base to relieve the work, and stops engageable todetermine the normal working position of said work support relative tosaid base, one of said stops comprising a 'slidable wedge and means toadjust said wedge to thereby vary the normal position of said worksupport.

2. In a machine tool, a tail stock having a relieving motiontransversely of its axis, a fixed tail stock base, an elongated andrelatively heavy but slightly resilient metal plate, means to rigidlysecure said plate to said tail stock and to said base, said plateforming the entire support for said tail stock on said base, and meansrotatably mounted in fixed bearings and effective to oscillate said tailstock on said plate and relative to said base to relieve the work.

3. In a machine tool, a tail stock having a relieving motiontransversely of its axis, a fixed tail stock base, a slightly flexiblesupporting member rigidly secured to said tail stock and to said base, aconstantly rotated cam, a roll engaged by said cam, a lever for said camroll freely pivoted on said tail stock, an abutment on said movable tailstock engaged by said lever, and means to selectively determine thesetting of said abutment, whereby said tail stock is oscillated on saidflexible supporting means by said cam to relieve the work to an amountpredetermined by the setting of saidabutment.

ERNEST A. WALKER.

